The invention is directed to a dental tool holder or handpiece for an endodontic file or filing worktool which is clamped in the tool holder so as to be secured against rotational and axial movements. A vibrating movement is impressed on the worktool.
Such root canal files are known from U.S. Pat. No. 4,571,183 and German OS No. 33 37 367. The file, according to the U.S. patent, executes a combined vibration transversely and longitudinally relative to the file which is particularly important. The oscillations or vibrations in the device according to the German OS are produced according to U.S. Pat. No. 4,330,278 or French Pat. No. 2,505,172 and are completely undefined, but noticeable longitudinal oscillations of the worktool always occur because of the geometry of the tool holder.
In addition to such filing tools, devices are known which work by means of oscillating rotational movement where an axial, swinging lifting movement can also be superimposed on this oscillating rotational movement. The amplitude of this movement is larger by several orders of magnitude than in the above-mentioned files. Because of the inherent rigidity of the filing tool, not all wall areas are reached in curved root canals, and, accordingly, cleaning can be carried out only insufficiently. When the thin filing tool is jammed in the canal, it can be twisted by means of oscillating rotational movement. In devices with swinging lifting movement, there is the additional risk that the base of the root canal will be pushed through and the tooth will be lost.
In filing tools of the type first mentioned, these disadvantages occur only to a limited extent. Until now, such worktools were excited with frequencies between 3 kHz and 20 kHz, that is, with high frequencies.
Accordingly, there is a disadvantage that the filing tool is easily overloaded and broken. Also, despite the high frequency applied to the filing tool, the amplitude of the oscillations observably decreases as the distance from the worktool holder increases when it is introduced into the root canal, i.e., only an insufficient cleaning effect is achieved in the lower area of the root canal. Moreover, there is the risk that the worktool will dig into the dentin and thus will drill its own, false canal.
The nerve canals in the human tooth have divergent anatomical forms. They are circular to sharply oval in cross section and straight to sharply curved in longitudinal forms. They have a varying quantity of outlets in the apex area, various lengths in the canal and sharp reductions in cross section in the apex area.